Hydrocarbon conversion processes and catalysts

ABSTRACT

SPECIFIED AMOUNTS OF ALUMINA ARE REMOVED FROM CERTAIN SILICA/ALUMINA CATALYSTS. THE PRODUCTS ARE IMPROVED XYLENES ISOMERIZATION CATALYSTS.

United States Patent HYDROCARBON 9 Claims ABSTRACT OF 7 THE DISCLOSURE Specified amounts of alumina are removed from certain silica/alumina catalysts. The products are improved xylenes isomerization catalysts.

This-invention relates to hydrocarbon conversion processes and catalysts therefor.

This invention is based on the discovery that the catalytic properties of certain silica/ alumina catalysts may be improved by removing from them a specified amount of alumina. It is believed that this effect may be due to removal of aluminawhich is not chemically combined with silica and which is present as alumina particles from a silica/alumina matrix, and/or to the creation of catalytically favorable sites on the surface of the catalyst by the removal, of alumina which is combined with silica from the surface of a silica/alumina structure. The treatment may also redistribute the silica and/ or alumina into a more catalytically favorable disposition. There may be a concomitant reduction in the alkali metal content of the catalyst and this is in general beneficial.

The invention comprises isomerizing an alkyl aromatic hydrocarbon in the presence of a. silica/alumina catalyst of which the alumina content has been reduced by from 1% to and preferably 720%, of the total alumina originally present, the catalyst comprising beforetreat ment'.7 to 40% by weight of alumina, and preferably 7 to 15% by weight of alumina and containing, aftertreatment, atleast 6% and at most 40% of alumina by weight. The alumina content of the catalyst may be .reduced by treatme nt with acids or complexing agents. Suitable acidsare those of which the anions serve to solubilize the aluminium by forming complex ions. Suitable acids include sulphuric acid, hydrochloric acid, hy-

drofluoric acid, hydrobromic acid, nitric acid and trihaloacetic acids (for example, trichloracetic acid) and mixtures thereof.

Suitable complexing agents comprisingchelating agents; for example, polar solutions (preferably aqueous solu-w tions) of ethylene diamine tetra-acetic acid or of acetyl acetone.

Many other complexing agents may be used especially in the presence of strong acids. 7

The above compounds will normally be used as solutions in, for example, water or an alcohol having 1 to 5 carbon atoms, for example, a monohydroxy alkane. Suit- T The catalyst may be contacted for from 1 minute to 1 p 3,793,384 Patented F eh. '19,

moles/ litre of the compound. The conditions of the treatment are chosen in the light of the desired amount of removal of the alumina. Contact of the'catalyst withthese solutions preferably takes place'a't a temperature in the range 0 to'200 C.'and very conveniently 15 to 100C; If desired the alumina content may be reduced in several stages, for example by repeated treatment with an aqueous solution of an acid. p

The alumina content of the catalyst may also be reduced by contacting it'with a gaseous material, for exam ple, hydrogen chloride or hydrogen bromide, which forms a volatile product with thealurnina'; The material is'preferably passed through a bed 0f the catalyst at an elevated temperature. 7 v

The alumina content of the catalyst may also be re duced by contacting it with a solvent as aforesaid, espe; cially Water, in the presence of a strongly acidic" ion" exchange resin. An acidic ion exchange resin may also be used'togcth'er with a solution of an acid.

After treatment the catalyst is preferably washed with water (particularly if a small volume of treatment solu- @by leaving the catalyst standing in water, for example at week with a solution of a compound capable of dissolving 3 the alumina, for example, a period of 10 minutes to 60 hours may be employed. The solution may contain 0.001

to 10 moles/litre and of the compound, and preferably 0.001 to 4 moles/litre, and more preferably 0.011 to 2 -100' C. for preferably 2 to 24!- hours, or by passing water through the catalyst bed, for example by treatment in Soxhlet equipment for similar times.

The catalyst before'treatment to reduce its alumina content is preferably a synthetic silica/alumina catalyst having a surface area in the range 50 to 700 square metres/gram, and more preferably to 300 square metres/ gram. Its mean pore diameter is preferably in the range 10 to 400, and more preferably 40 to 300 A. l

The catalyst may, if desired, by contacted with liquid water at a temperature above C. This is preferably carried out before, or, when an aqueous solution is to be used, during the treatment to reduce its alumina content. In the latter case great care should be taken not to remove more than- 35% of the alumina as this readily occurs and reduces the performance'of the catalyst. Suit-' able methods of treatment are disclosed in our patent application No. 91,194.

It is preferred to isomerize alkyl benzenes having at most 4 carbon atorns in each alkyl group, especially the xylenes.

.According to a preferred form of the invention one or more xylenes containing less than an equilibrium concentration of paraxylene are isomerized toproducefa producthaving a higher concentration of paraxylene. Such xylenes may, for example, be mixtures of metaxylene together with ethyl benzene, orthoand/or paraxylene.

According to a further form of ,the invention one or more xylenes containing less than an equilibrium amount of orthoxylene are isomerized to produce a product having a greater concentration of orthoxylene.

The isomerization of xylenes is preferably carried at a pressure of 1 to 5 atmospheres absolute. It is preferred to'carry out the isomerization in the presence of 100 to 10,000 parts per million of steam by weight based on the xylenes. a

It has been found that especially good catalysts are producedby treatment with nitric or hydrochloric acids or with ethylene diamine tetra-acetic acid. Such vcatalysts generally have satisfactory activities and selectivities in catalyzing the desired isomerization reaction rather than undesired disproportionation reactions in the isomerization of alkyl benzenes and may also be less prone to out at a'temperature in the range 200 to 500 C., and preferably 300 to 500 C. It is preferably carried out at a pressure of 0.5 to 50 atmospheres, and more preferably I cfar b'oniza'tion which necessitates regenera 1011 by burning EXAMPLE 4 ff.carb n eousdenosits.

. ple (30 of the same catal st as used in Ex- .Amorphous slhca/alummgiecatalyst whlch the ample 3 was treat d with 256ml. of a OYIO molar aqueous mina content has been reduced as prev1ously described Solution of HF for 24 hour; at room temperature This EaW -WQ gnd F' lt9 bg'nseful 5 treatment removed 8% of the aluminum present and the 9 yi i l ab vs w e tr hydr-ogamqn"-conversmn sodium.content was reduced from 0.09 to 0.085% by p ocesses whi ch are catalyzed-bywacrds, for-. e)gample, -p 7 Y J :1 'clging, allgylation, dealky latiori and isomerizatiQnJIhey I I 5; also nsefulas supports for,hydroisornerization cat- I I I} I "Ag-sample (30 g) of'thesamecatalyst as usedin Examand rejformingc atalysts,..- II I I I M p I v f I I I III I I I p163 wastreat'edwith 225' ml. of" a 0.73 molar aqueous "EXAMPLE' I II solutiod'ofHBr for- 24'hours at room tempeirature. This 'jeichiyiarefsl BQs arns Olf a silica /aIumina atayantva an anal sis a nt removed 9 th alw nu P e iafldthe f and90(%/ silica a surface amaIof I sodium content was. reduced from to 0.04% .by

.7 a olum 0 .g-. in the. form, Y 5 v 0 4 mm..,b d was adde d -;to 225 m1. of an aqueous solu- H I I EXAMPLE-"6 I t IQ I I v,qontam g 0.84 mole of hydrogen chloride/litre. Each of the catalyst (12 g.) described in Examples '2 After Standlng 24 houfs room temperature t to 5 and they starting materialweretested for performance l .:l %$,,.fi fld Id dI nn at- 2 7- for in orthoxylene isomerization as described in'Example 1. 15 s.-,; nalys is of the solution showed'that 15% of- The following table gives the feed rate and "the'efiluent the} alumina-had, been removed vfrom the catalyst. The composition after6'hours on-line. Y

' I I Untreated, Ex. 2, Ex.3, Ex.4, Ex.5, Flow rate Q; otli'quidhn 10.4 1 7.7 16.0 I 2 17.2

Mo es percentin eifluent 01-. I Y araxy1ene. 8.6 9.8 11.2 10.9 9.0 1. Metaxylene. 36.1 37. 8 40.7 40.7 37.0 III Toluene I 2.0(5) 2.1 2.6 a2 .2.0 I Paraxylene/toluene 4.2 4.7 4.3 3.4 4.5

sodiumcontent was reduced in this treatment from 0.09 Asibefore trimethyl benzenes were observed in amounts to. 0.04% by weight. equal to the amount of toluene in each case- It will be Samples (12 g.) of the .treated catalystand the starting observed that each of the treated catalysts is much more material were evaluated as follows: Each was packed into active, than the untreated material and apart fromExama. .tubular glass. reactor and maintained at 550 C. in a pie 4 (the HF treated catalyst) are more selective for isostrearn of-air for 14 hours. The reactor was then flushed merization relative to disproportionation.

rltrogen for about minutes before cooling to EXAMPLE 7 Orthoxylene (99.5% pure containing 0.2% toluene, 30 g. sample of a srhca/aluminabead catalyst .con- 0.1% paraxylene and 0.2% metaxylene) was fed to the talnlng 0% alumma and havmg a Surface area of 186. reactor as a vapor at a temperature of 450 C. and at.- and a P Volume O t a o h ri r s r Th flow rat and the nt f with 1.3 l. of a saturated solution of EDTA- in waterthe products in the effluent stream after 6 hours ineach under "refiuX at 100 C. for 48 hours. The resulting ma- 5 terial was filtered, washed and dried in a stream of air case is. given in the, following table. I I

at 200 C. This treatment removed about 15% of the l gf g II l fgfg reduced from 0.09 to 0.05 by weight.

' Both the treated catalyst and the sta'rting material were 50 tested for performance ,in orthoxylene isorne rization as Flow rate (ml. of-liquid hr.

Moles percent in efliuent of Paraxylene. -7,'8 10.1 et lenea2. 1 36.1 dF SCIIbQd IH EXamPR 1. The flow rates and the cornglg gggf Z13 P i n f he n f r 6 hours on-line are given thefollowing table, I

TrirnethyLbehzenes are also observed in amounts ap; I

Untreated Treated aluminum in the catalyst'and the sodium content wasv proximately equalv to the amount of toluene in each case. 0 It is clear that the activity of the treated catalyst is much Flow rateqnl. otliqutd hr. 19.1 I 2. 2' greater than that of the untreated material, while the Molespmentin emuenf selectivity is. unchanged. L I Paraxylene 10.4 9.1

EXAMPLE 2 V i I. Paraxg'lene/tblhehe 4:2 4:2 A sample (300. g.) of a similar bead catalyst tofthat I v used in Example 1 buthaving a surface area of 140 I As before,.trimet hyl benzenes were formed in amounts m? g. and a pore volumee of 0.55 cm. gwas treated equal toth'e amount of toluene. The results show that the I in" a similar manner with 2.25 l. of a 0.75 molar aqueous f treated catalyst is much more active. than untreated cata solution of HCl. During the treatment the catalyst lost lyst'but has the same selectivity. 13% of its aluminium content and the sodiumcontent was I I reduced from 0.09 to 0.05% by weight. EXAMPLE 8 EXAMPLE 3 1 I A13 0g. sample of a silica/alumina bead ca'talysti con- -taining 10% "alumina and 'having a surface area of 1 08 'A sample (30 of an identical catalyst "to that demFgr and a porelvolum'e of 0.55 cmfigfl was treated scribed in Example 2 was treated with'225inl. of-"a 0.4 at 100 C. for48 hours with 200 mls. o fa saturated solumolaraqueous solution ofHCl at 100 C. under reflux tionin w'ate 'rat' EDTA. By EDTA is meant ethylene "di j for'6 hours'IThis treatment removed about 25% bylweight' amine tetraac'eticacids." The treatedmaterial was then' I of'the aluminium content'of the catalyst and the's'odium" .;;filtered off, washed and dried at 200 C. "in astr'eam'bf content was reduced from 0.09 to"0.03'%'by'weight; air; This treatment removed 1% of the aluminium inrthe' 5 catalystand the sodium content was reduced from 0.09 to 0.07% by weight.

Both the treated and untreated catalyst were tested for preformance in orthoxylene isomerization as described in Example 1. The flow rates used and the composition of the efiiuent after 6 hours on-line are given in the following table.

. V Untreated Treated 7 catalyst, catalyst, Flow rate (ml. of liquid hr. 7.0 11. 4

Moles percent in efliuent of- Paraxyl 10. 1 12. 2 Metaxylene 38. 2 41. 1 Toluene-.- 2. 5 2. 4 Paraxylene/tolue 4. 1 5. 1

EXAMPLE 9 Flow rate (ml. of liquid hr.

Moles percent in efiluent oi- Paraxylene- 9. Metaxyl 32. Toluene. 1. 9 Paraxylene/toluene 4. 7

This catalyst, prepared by the combined treatment, was much more active than thatprepared by simple EDTA treatment described in Example 8.

EXAMPLE A sample (50 g.) of silica/alumina bead catalyst containing 10% alumina and having a surface area of 450 mflgf and a pore volume of 0.52 cmSg. was treated at204 C. for 4.5 hours in liquid water saturated with EDTA. The resulting material was filtered and dried at 200 C. It had a surface area of 195 m. g. and a pore volume of 0.54 cm. g.,-

Both the treated and untreated material were tested for performance in othoxylene isomerization as described in Example 1. The feed rate used and the composition of the efiluent in each case is given in the following table:

Untreated Treated catalyst, catalyst,

Flow rate (g. of liquid hr. 26. 5 14. 4

Moles percent in effluent of- Paraxy ne 9. 6 9. 7

Metaxylene--. 34. 6 35. 5

Paraxylene/toluene 'Trimethylbenzenes were formed in amounts equal to the amount of toluene. The table shows that although the treated catalyst is less active than 'the starting mate rial it is much more selective towards isomerization.

EXAMPLE 11 The resulting catalyst and the starting material were tested for performance in orthoxylene isomerization at 450 C. as in Example 1. The flow rate used and the product compositions are given in the following table:

Treated Untreated catalyst, catalyst,

Flow rate (ml. of liquid hr. 10. 4 22. 1

Moles percent in effluent of Paraxylene 8 6 8.7

Metax 36 1 35. 9

Toluene 2 1 1.9

Paraxylene/toluene 4 1 4. 6

Trimethyl benzenes were also observed in amounts approximately equal to the amount of toluene in each case. It is clear that the treated catalyst is much more active and has a higher selectivity towards isomerization.

' EXAMPLE 12 300 g. of silica/alumina catalyst having an analysis of' 10% alumina and silica, a surface area of 140 m. g.

and a pore volume of 0.55 cmF/g. in the form of 4 mm. beads, were added to 2.25 l. of a 0.75 molar solution of I-ICl. After standing for 24 hours at room temperature,

the catalyst-was filteredand dried at 200 C., thencalcined at 550 C. Analysis of the treating solutionshowed that 13% of the alumina had been removed from the catalyst. The sodium content was reduced in the treatment from 0.09 to 0.05% by weight. r I

EXAMPLE 13 330 g. of a similar bead catalyst to that used in Example 12 were treated with 2.2 l. of a saturated solution of EDTA in water (i.e. 0.034 molar) under reflux at C. for 48 hours. The resulting material was filtered, washed 25.5%). Weight hourly space velocity (WHSV) was adjusted to give a constant proportion of paraxylene in each reaction product. Water was fed to the reactor at the stated rate. Details of the runs performed are given in the following table.

Untreated Ex. 12 Ex. 13

Water (ppm. vJv.) added to feed. 700 900 900 SV; 1. 56 2. 58 2. 41 p-Xylene in product 17. 5 17. 5 17. 3 Xylenes converted to other mat 3. 1 3. 5 2. 9

Average of 4 samples taken after 3, 6, 9 and 12 hours online respectively. 1

It can be seen from these results that the treated catalysts are much more active than the untreated catalyst,

but selectivity is the same in each case (within the limit of experimental error) EXAMPLE 14 A silica/alumina catalyst having an analysis of 10% by weight alumina, a surface area of 130 mF/g. and a pore volume of 0.55 cm. /g. in the form of 4 mm. beads,

was treated with beads of B35 mesh size 14 to 52 of an ion exchange resin of the sulphonated polystyrene type sold by British Drug Houses Limited. under the trade name Amberlite Resin IR (H) as follows; 400 g. of the catalyst and 400 g. of the resin were added to 2 liters of distilled water and the mixture was boiled for 7 hours. The resin was then separated from the catalyst by Washing on a sieve with distilled water and the catalyst was dried at 200 C. when calcined at 550 C. in a stream of air. Analysis of the resin showed that 6% of the alumina originally present had been removed from the catalyst, i.e. the final alumina content was 9.4% by weight. Thesodium content was reduced from 0.09% to 0.02% by w t Q V H The treated and untreated catalysts were compared for performance in xylenes isomerization at 450 C. and 1.5 bar's pressure absolute. Ineach case the feed had-the following composition (percent by weight).

Toluene 1.04

Ethylbenzeii 1-; 8.6 Paraxylene a 8.5 Metaxylene 55.0

Or-thoxylene 25.5

Water was injected at a rate o'f'1,000 parts per million base don the feed. Weight hourly space velocity (WHSV) was adjusted to give the same paraxylene concentration in each product. Details of the runsare given in the following table:

Untreated v Treated W'HSV (hr.- l 1. O6 1. 73 Paraxylenein product 1 (percen 17. 8 17. 8 Increase) A p (percent) 9. 3 9. 3,

Xylenes converted to other materials) Ax (percent) 4. 1 3. 8

1 Average for 4 samples taken after 3, 6, 9 and 12 hours on-line.

The above figures show that the treated catalysts was 63% more, active than the untreated catalyst.

EXAMPLE 15 grams of the same silica/alumina catalyst used in Example 1 were added to 225 mls. of a solution containing 0.57 mole of hydrogen chloride per liter instead of the solution containing 0.84 mole hydrogen chloride per liter. After standing for 24 hours at room temperature the catalyst was filtered and dried in an oven at 200 C. for 15hours. 7

Samples (12.0 grams) of the treated and untreated catalyst were tested for performance in orthoxylene isomerization as in Example 1. The feed rates and product compositions obtained after 6 hours on-line are given in the fol lowing table:

Untreated Treated 7 a r 7 catalyst, 7 catalyst, Flow rate (g. hr. 13. 2 1 .0

Moles percent in Eflluent of Para-xylene 7.8 11. 8 -Metaxylene-; --32.1- 39.8 .Toluene 1.9 2.8 Paraxylene+toluene by moles 4.2 4. 2

Trimethyl benzenes were also observed in amounts approximately equal to the amount of toluene in each case. It is clear that the activity of the treated catalyst is much greater than that of the untreated catalyst, while the selectivity is unchanged.

EXAMPLE 16 A catalyst identical to that of Example 1 but which had.

been-exposed to liquid water at 198 C. for 24 hours and. having after this treatment a surface area of 133'square meters per gram and a pore volume of 0.54 ml./ gram was treated in the same manner with a 1.03 molar solution of hydrochloric acid. 13% of the A1 0 present and about of sodium were removed. 1

Both the treated and untreated catalysts (12 grams) were tested for performance in orthoxylene isomerization' as in Example 1. The feed rates and product compositions Trimethyl benzenes were also observed in an'amount approximately equal to the amount of toluene. It may be" observed that the treated catalyst is much-more active and significantly more selective for isomerization thanthe' untreated catalyst." e

EXAMPLEv 17 30 grams of a silica/alumina bead catalyst containing 10% alumina and silica and having a surface area of m. g. and a pore volume of 0.52"m. "gwere added to 22:5 mls. of an aqueous solution containing 3.0 moles of nitric acid per liter. After standing for'2'4 hours at ambient temperature the solution was drained out and the catalyst washed 3 times by soaking in 22 mls. of cold water for 24 hours. Analysis of the acid solution and the washings indicated that 13% of the alumina had been re-' moved m h cata yst- .Th sodi m contentwasrcduced...

from b.09 to 0.04% by weight.

Samples (12 g.) of the treated and untreated. material were evaluated for performances in orthoxylene isomeriza-- tion at 450 as described in Example 1. The How rate and the amounts of the products in the effluent in each case is given in the following table.

Untreated catalyst catalyst Flow rate (ml. of liquid hr.- 10. 4 23. 2

Moles percent in efliluent ofi V Paraxylene 8. 6 9. 17 Metaxylene 36. 1 36. 57 Toluene 2.1 1. 83 Paraxylene/toluene 4. l 5. 0

Trimethyl benzenes were also observed in amounts ap e proximately equal to the amount of toluene in eachcase The treated catalyst has a greater activity anda higher selectivity towards isomerization. g

Spent silica/alumina catalysts containing substantially 7 to 49% by weight of alumina which have previously been used in alkyl aromatic hydrocarbon isomerization processes may sometimes with advantage be treated to remove 1 to 35%, and preferably 7 to 20% ofthe-total alumina present to give a catalyst containing at least 6% and at most 40% of alumina. 7

1 What is claimed is:

1. A process which comprises an alkyl aromatic hydrocarbon in'the presence of an amorphous silica/alumina catalyst of which the alumina content has been reduced by from 1% to 35% of the total alumina originally present, the catalyst having before treatment'a surface area in the'range' "50"to 700 's ua're'nieters/gmm and a mean pore diameter in thetrange 10m 400 A. ancl;.com-

prising before treatment substantially 7 to 40% by weight; of alumina and containing after treatment, at least 6% by weight of alumina.

2. A process as claimed in claim .1 in which the alumina content has been reduced by from 7 to 20% of the total alumina originally present... I 3..A process as claimed in-claim 1 in which the catalyst comprises 7 to 15% by weight of aluminaibeforetreat-.

'4. A process as claimed in claim 1 in whichthee alumina content of the catalyst has been reduced by treatment with acids or complexing agents. 1 x

5. A process as claimed in claim 4 in which the" acid or: complexing agent is used as ausolution in water or'an alcohol having 1 to 5 carbon atoms.

Treated 6. A process as claimed in claim 1 in which catalyst has been contacted with liquid water at a temperature above 100 C.

7. A process as claimed in claim 1 in which one or more Xylenes containing less than an equilibrium concentration of paraxylene are isomerized to produce a product having a higher concentration of paraxylene.

8. A process as claimed in claim 1 in which one or more xylene containing less than an equilibrium amount of orthoxylene are isomerized to produce a product having a greater concentration of orthoxylene.

9. Amorphous silica/alumina catalysts of which the alumina content has been reduced by from 1% to 35% 0f the total alumina originally present, the catalyst having before treatment a surface area in the range 50 to 700 square meters/gram and a mean pore diameter in the range 10 to 400 A. and comprising before treatment, substantially 7 to 40% by weight of alumina and containing, after treatment, at least 6% by weight of alumina.

References Cited UNITED STATES PATENTS 3,116,973 1/1964 Haden 252-450 3,130,170 4/1964 Stover et a1 252450 3,350,098 8/1967 Haden et a1. 252450 3,691,099 9/1972 Young 252455 Z CURTIS R. DAVIS, Primary Examiner US. Cl. X.R. 260-450 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3 r 793 [384 D d February 19 1974 Inventor) John G. Chenoweth, Ivan J. S Lake Roy J. Sampson,

Paul Osmond, and Douglas Shooter It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

In claim 1 line 1 at column 8 line 54 after "comprises" insert -isomerizing- Signed and Scaled this Arrest.-

RUTH C. MASON Arresting Officer C. MARSHALL DANN Commissioner nfPalents and Trademarks 

